U02BALost Communication With Hybrid/EV Electronics Coolant Pump B
- Generic OBD-II code · Network
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- Needs a drive cycle to confirm a fix
- How the car detects it
- Hybrid and electric cars cool their power electronics, such as inverter, DC/DC converter and on-board charger, with electric pumps that hang on a LIN line and report their state to a thermal or vehicle controller. U02BA means pump B of that loop no longer answers. No manufacturer documents U02BA publicly or says which pump bears the letter B. Stellantis shows the layout on the 2024-2025 Dodge Charger and Jeep Wagoneer S: three identical pumps, each with its own software and its own LIN bus to the EVCU; without a master message a pump falls into an emergency mode at full speed and can drain the 12 V battery (STAR S2508000056). GM's 2011 Volt wired pump A directly and rated its circuit fault P0CE9 as Type B. With pump B silent the electronics run hotter and drive power may be cut.
- What you may notice
- Warning for the hybrid/electric drive system, MIL possible
- Reduced drive or charging power when the electronics warm up
- Pump running constantly or not at all, 12 V battery drained
- Likely causes
- LikelyLoose or corroded pump connector, open or shorted LIN wire
- PossiblePump power supply or ground missing (fuse, relay, ground point)
- PossiblePump electronics failed or pump seized
- RarePump of another position fitted or controller software outdated
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Hard · Usually a job for a workshop.Typical cost: €80 – €900
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.